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Continuous positive airway pressure, CPAP

Continuous positive airway pressure (CPAP) machine, ResMed S9 Elite™ model

CPAP means Continuous Positive Airway Pressure

Several continuous positive airway pressure machines are available on the market. The goal of this page is not to indicate which one is the best machine, but rather inform how a continuous positive airway pressure (CPAP) machine can be efficient in sleep apnea therapy.


Reduction of daytime sleepiness is observed after using this machine for a first night and benefits continue to increase during subsequent nights up to 6 weeks later.

Resolution of daytime sleepiness is even more important in patients having an apnea-hypopnea index (AHI) higher than 30.

Does CPAP make a difference?

Individuals suffering from apnea experience a reduction of their cognitive skills and their overall performance. The use of CPAP improves cognitive skills and neurobehavioral performances of individuals suffering from apnea.

Improvements will be especially more important if the machine is used for a minimum of 6 hours per night or more.

A CPAP machine helps decrease arterial pressure by 1 to 2.5 mm Hg. It is not much, but it is statistically significant and clinically important.

CPAP therapy is associated with a reduction of 64% of cardiovascular risk, independently of age or pre-existent comorbid cardiovascular conditions. CPAP is thus recommended as a supplementary therapy for the reduction of arterial pressure in individuals with apnea suffering from arterial hypertension.


The main disadvantage of a CPAP machine is adherence to therapy. The longer the machine is used during a night’s sleep, the better is the reduction of daytime sleepiness, the better is the improvement of behavioral performances, the better is vigilance and the better is the effect on the reduction of arterial pressure.

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Is it bad to have poor adherence to therapy?

Basically, we must understand that CPAP therapy will be efficient if the machine is used. Irregular use over a short period cannot be efficient in obstructive sleep apnea therapy and in its harmful effects on human beings.

Those who have good adherence to CPAP therapy uses CPAP 6 hours per night’s sleep in average. Those who skip a night use it only 3 hours per night in average.

In other words, a patient who does not follow well his CPAP therapy, not only does he not use it every night, but when he uses it, the duration of use is shorter than the one who uses it regularly every night.

People who follow well their therapy use it adequately the first night and maintain their behavior. Those who skip nights during the first week are those who will become irregular users.

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Which CPAP dosage results in health improvement?



Cumulative effect of hours of CPAP use in obtaining normal daytime awakening and vigilance level.

According to Weavers TE, Maislin G Dinges et coll. in their study composed of 129 participants after 3 months of CPAP use, improvement of daytime sleepiness symptoms (better daytime awakening) measured using the Epworth Sleepiness Scale (ESS) and reported by the patient is obtained when the machine was used at least 4 hours per night. The Multiple Sleep Latency Test (MSLT) gets back to normal when CPAP is used for a period of 6 hours per night. The MSLT, measured with a polysomnography, is the time it takes to fall asleep on a 20-minute period during the day. The one who falls asleep in less than 5 minutes has a sleepiness problem. 10-minute latency is considered normal.

The Functional Outcomes of Sleep Questionnaire (FOSQ) measures vigilance and sleepiness state. Vigilance becomes normal if the participant uses CPAP for a period of 7.5 hours per night.

Thus, a relationship exists between the duration of use of the CPAP machine and the reduction of sleep apnea symptoms, the improvement of awakening or daytime vigilance and the increase in sleepiness latency time.

This research shows that a great percentage of patients will be able to function normally during the day if CPAP is used for a long time (at least 7 hours) during their night’s sleep.


Boyd SB et Walters AS in an article of the Journal of Oral and Maxillofacial surgery 2012 (JOMS) conducted a study with a group of 37 individuals of 44 ± 9 years of age in average and a moderate to severe apnea-hypopnea index (AHI) of 56.3 ± 22.

Results show a reduction of the apnea-hypopnea index (AHI) if the patient adheres well to CPAP therapy. In reality, to reduce an AHI to a value of 5, it takes an adherence of 99%. If adherence to CPAP therapy is 79%, the AHI can reach 15. In reality, for a patient having an AHI of 30 to 60, it takes adherence to CPAP therapy of more than 90% to reduce the AHI to a range of 5. If adherence to CPAP therapy is between 58% and 81%, the AHI will be 15.

Every individual of the group then underwent a simultaneous maxillomandibular advancement surgery. Such a surgery was able to reduce the AHI to 11.6 ± 7 for these individuals. To obtain a similar result with CPAP, it takes an 86% adherence to CPAP therapy.

Efficiency of CPAP in the reduction of the AHI versus the percentage of adherence to therapy. © Boyd and Walters. Apnea-Hypopnea Index in the Home Setting. J Oral Maxillofac Surg 2012.

The figure on the opposite side shows the reduction of the apnea-hypopnea index (Y axis) versus the percentage of CPAP use. A percentage of use of 75 to 100% is necessary to reduce an AHI of 60 to a level lower than 15.

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Patient using a CPAP machine with 2 different masks

Philips System One CPAP machine and ResMed Mirage™ FX nasal mask

Courtesy of a patient who no longer wishes to use his CPAP machine and who decided to begin a major orthosurgery treatment, here is a System One CPAP.

Nasal facial mask

ResMed Mirage™ FX nasal mask



Facial mask for CPAP, Philips Amara model

Oronasal mask




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